Method and apparatus for treatment of nongaseous materials



July 3, 1934. D. D. PEE'IBLES Filed June 10. 1931 .36 6

4 Sheets-Sheet l Eur/woe 4 METHOD AND APPARATUS FOR TREATMENT OFNONGASEOUS MATERIALS IN V ENTOR. Dawn 2 fise es w ATTON Y.

, July 3, 1934. D. PEEBLEs 1,964,858

METHOD AND APPARATUS FOR TREATMENT OF NONGASEOUS MATERIALS FlEl 4;INVENTOR.

AT'M 'Y.

Patented July 3, 1934 UNlTED STATES METHOD AND APPARATUS FOR TREATMENTOF NONGASEOUS MATERIALS David D. Peebles, Eureka, Calif.

Application June 10, 1931, Serial No. 543,315 In the Netherlands January12, 1931 9 Claims. (01. 159 4) This invention relateslgenerally tomethods and apparatus for effecting desiccation or other treatment ofnon-gaseous materials by contacting the material, while in suspension individed con- 5 dition, with a suitable gaseous medium. The treatment'may be for any one of a variety of purposes, and may in general be anytreatment in which it is desired to effect intimate and prolongedcontact between the non-gaseous material and the gaseous medium.

A particularly advantageous application of this invention is in thedesiccating of non-gas eous materials consisting of solid or liquidmaterials contained in solution or suspension in an aqueous or otherliquid material, and especially in cases where the solid or liquidconsists in part or wholly of organic material or material susceptibleto injury by heat, for example in the desiccation of milk, or of-milkproducts, such as whey. The terfi Tlesiccatio n as used herein is to beunderstood as including the partial or complete evaporation of Water orother liquid from any such material, and while it is customary in manyoperations to remove sufficient liquid to produce a substantially drysolid product, the term desiccation as used herein is not to beunderstood as so restricted, as the liquid may be only partially removedso as to effect merely a concentration rather than an actual completedrying of the material.

The invention in its broadest aspects is not restricted to the treatmentof organic materials nor to the desiccating of material, as it may alsobe used to good advantage for many other purposes.

This application is a continuation in part of my application Serial No.375,640, filed July 3, 1929.

Certain features of the preferred form of the invention herein disclosedare shown and claimed in my copending applications Serial Numbers164,991 (now Patent No. 1,830,174) and 293,198 (now Patent No.1,914,895). In application No. 164,991, I have disclosed a novel form ofdesiccating apparatus utilizing a plurality of nested vortexes orcyclonic movements of gas within an inclosed treatment chamber.Application No. 293,198 discloses a somewhat similar apparatus in whichone of the vertexes or cyclonic movements of air is maintained byrecirculating a gaseous medium into the treatment chamber. It ischaracteristic of the apparatus and methods disclosed in thoseapplications that desiccation of organic material can be carried outwith a relatively small compact apparatus, and without deleteriouseffect on certain organic material subject to injury by prolonged heattreatment. In operating apparatus of this character for the dehydrationof certain organic materials, as for example milk, I have observed thatthe dehy- 0 drated product frequently contains dark particles which haveapparently been carbonized by heat. Dark particles of this kind arefrequently objectionable, particularly where the product is used as afood for human consumption. I have discovered that the formation ofthese carbon ized particles is due to the contact or accumulation of acertain amount of the material being desiccated, upon surfaces or partsof the dehydrating apparatus which are heated to relatively 7 hightemperatures.

It is an object of the present invention to devise a dehydratingapparatus and method which can be used in the dehydration or othertreatment of milk, or other material susceptible to 7 injury by heat, bycontact with a gaseous medium at relatively high temperature without theformation of carbonized, burned or otherwise injured particles.

A further object of the invention is to provide for treating the dividednon-gaseous material with a gaseous medium at a relatively hightemperature, while preventing detrimental contact or accumulation ofnon-gaseous material being treated on surfaces or parts which are ofnecessity heated to a relatively high temperature by such gaseousmedium.

It is a further object of this invention to provide for desiccation ofmaterials subject to injury by heat, by means of a gaseous drying mediumat relatively high temperature into which such material is introduced individed or atomized condition, while at the same time providing meansfor cooling of interior surfaces of parts of the apparatus which aresubject to heating by said gaseous drying medium.

A further object is to provide for desiccation of materials susceptibleto injury by heat, by introducing such materials in divided or atomizedcondition into a gaseous drying medium at relatively high temperature ina central zone within a desiccating chamber, while maintaining an outerzone of gaseous medium at relatively low temperature serving to blanketthe walls of said chamber and to prevent heating thereof by therelatively high temperature drying medium, the gas in said outer zonebeing maintained at a sufficiently low temperature to keep theperipheral wall of said chamber at a temperature below that at whichinjury would be caused to particles of said material coming in contacttherewith. The central high temperature zone and the outer lowtemperature zone are preferably maintained by causing swirling movementof the gas therein, and the swirling movement is preferably in oppositedirections in the respective zones.

It is a further object of this invention to devise an apparatus for theabove-mentioned purpose having novel means for actuating a mechanicalscraping or cleaning mechanism thereon.

Other objects of the invention will be pointed out hereinafter or willbe evident from the following description.

According to this invention, the non-gaseous material to be treated isdelivered in atomized or finely divided condition into the centralportion of a treatment chamber, and a quantity of gaseous medium isdelivered into a position adjacent the center of said chamber so as toreceive the non-gaseous material so delivered and cause the same tobecome suspended therein, while one or more additional zones or gaseousmedium are also maintained within said treater chamber and in nested orconcentric arrangement about said first named gaseous medium, and thenon-gaseous material is caused to pass outwardly and progressivelythrough the gaseous zones thus defined, so as to effect the desiredtreatment by contact of the gaseous medium with such non-gaseousmaterial, the resulting non-gaseous product being retained in dividedcondition and being preferably removed from the chamber in suspension ina portion of the gaseous medium and conveyed thereby to any suitablecollecting means. The non-gaseous material is preferably delivered intothe treatment chamber with an initial outward component of motion, forexample, by means of centrifugal atomizing means, and the gaseous mediumin the respective zones is also preferably caused to whirl or to have avortical motion so as to impart a further centrifugal action to thesuspended non-gaseous material therein, whereby the outward motion ofthe non-gaseous material is caused to be effected by means ofcentrifugal action.

Furthermore, the gaseous medium in adjacent concentric zones ispreferably caused to whirl in opposite directions, in order to providecertain advantages in operation, as hereinafter pointed out.

In the preferred embodiment of this invention, the whirling motion ofthe gaseous medium in the outer zone is maintained by continuallyremoving a portion of the gas from a point in said outer zone andcontinually re-introducing the same with a substantially tangentialcomponent of direction adjacent the periphery of the treatment chamber.The portion of gas thus utilized for recirculation may be removedseparately from the portion of gas which is continually removed for thepurpose of eventually conveying the treated non-gaseous material insuspension out of the treatment chamber to suitable means for collectingsuch material, or both of these portions of gas may be removed togetherand then divided by suitable means. Furthermore, if desired, a portionof the gas removed from the chamber may be passed through collectingmeans for removing suspended material therefrom and may then be returnedto the treating chamber for recirculation.

When the invention is applied for the purpose of desiccation, thegaseous medium introduced adjacent the central portion of the chamber,and with which the introduced non-gaseous material first comes intocontact, is at a relatively high temperature, while the gaseous mediumin the outer zone is maintained at a relatively low temperature forreasons fully explained hereinafter. The incoming high temperaturegaseous medium tends to cause the adjacent parts of the apparatus, andparticularly the walls defining the passage through which it isintroduced, to become heated to a relatively high temperature.Furthermore, the introduction of this gaseous medium, together with thewhirling motion of the gas in the concentric zones, tends to cause eddycurrents of gas. As a result, it has been found that, in the drying oforganic materials or other substances susceptible to injury by heat,portions of such material tend to be moved by such eddy currents intocontact with these heated walls or other parts adjacent the hot gasinlet passage, thus causing burning, discoloration, or other injury tothe product, such as to either render the same unsaleable or of aninferior quality. This is particularly true, for example, in the case ofmilk or milk products. According to this invention these injuriouseffects are eliminated by introducing air or other gas at relatively lowtemperature, in relatively small amounts, adjacent the hot gas inletpassage and in such positions as to prevent contact of the dividednon-gaseous material with walls or other parts of dangerously hightemperature. Furthermore, the relatively low temperature gas thusintroduced at these points serves to cool the adjacent parts of theapparatus and to somewhat reduce the temperature to which such parts areheated by the high temperature drying medium.

Further features of the method and apparatus of this invention may bebetter understood by reference to the accompanying drawings whichillustrate, by way of example only, certain specific embodiments of saidinvention. Referring to these drawings:

Fig. 1 is a vertical section of a desiccating or treating chamber andcertain apparatus associated therewith, adapted particularly fortreatment of liquid containing material, taken on line 1--1 in Fig. 2,but partially in elevation.

Fig. 2 is a plan view of said treating chamber together with one form ofmeans for supplying gaseous medium thereto and for removing the sametherefrom, and for effecting recirculation of gaseous medium in theouter zone.

Fig. 3 is an enlarged vertical section of the upper portion of thetreating chamber, showing the means for introducing non-gaseous materialto be treated and for introducing the gaseous medium into said chamber.

Fig. 4 is a horizontal section on line 4-4 in Fig. 3.

Fig. 5 is a section on line 5-5 in Fig. 4.

Fig. 6 is a partial view of the lower portion of the treating chambershowing a modified form of the means which may be provided for removingany material which may be deposited on the sides and bottom of thetreating chamber.

Fig. 7 is a plan view of an installation showing a modified means ofheating the gaseous medium delivered to the treating chamber and also amodification in the means for effecting circulation and removal ofgaseous medium therefrom.

Figs. 8 and 9 are plan and elevation views respectively of another formof installation embodying this invention.

Fig. 10 is a vertical section of the treatment chamber shown in Figs. 8and 9.

of said chamber.

Fig. 11 is a horizontal section on line 11--11 in Fig. 10.

Fig. 12 is a detail of the atomizing means and adjacent parts, of theapparatus shown in Figs. and 11.

Referring to the form of apparatus shown in Figs. 1 to 5 inclusive, atreating chamber is indicated at 1, said chamber being of substantiallycircular horizontal cross-section, for example a cylindrical vesselhaving a substantially vertical axis, and being provided with top andbottom walls 2 and 3 respectively. This particular apparatus is intendedespecially for the drying or desiccation of divided non-gaseousmaterials, and for this purpose means are shown for supplying a hotgaseous medium to the chamber 1 adjacent the axis thereof, such meanscomprising a furnace 4 of any suitable type and fired with any suitableform of fuel, a flue or conduit 5 for conducting hot combustion gasestherefrom, a branched distribution conduit 6 connected to flue 5 andextending over the top wall 2 adjacent the central portion thereof, adistribution chamber '7 formed between the top wall 2 and afrustoconical partition 8 and communicating with the conduit 6 by meansof a suitably shaped opening 9 in said top wall, and helically inclinedvanes 11 located in the annular opening 12, of considerably smalldiameter than chamber l, leading from the distribution chamber 7 intothe interior The vanes 11 extend substantially radially as shown in Fig.4, and are preferably inclined downwardly in one directioncircumferentially, as shown in Fig. 5, so as to provide inclinedpassages 13 therebetween through which the gaseous medium is introduceddownwardly and with a whirling or vortical motion into the chamber 1.

A cylindrical or other suitably shaped conduit 15 extends centrallythrough the distributing chamber 7, communicating at its upper end withan opening 16 in the top wall 2 and having an opening 1'? at its lowerend leading into the chamber 1. Suitable means are provided forintroducing non-gaseous material to be desiccated through the conduit 15and for delivering the same outwardly in atomized or divided conditioninto the whirling gaseous medium delivered into the treating chamber asabove described. Such means are shown as comprising a centrifugalatomizer 18 of any suitable type mounted at the lower end of a shaft 19which extends through and is rotatably supported on an inner housing 20and which is provided at its upper end with suitable driving means suchas pulley 21 mounted on said shaft. Said pulley may be driven atsuitable speed for effecting the desired atomization, by means of anelectric motor 22 operatively connected thereto by means of pulley 23and belt 24. The housing 20 together with the shaft 19 and atomizer 18may be supported by means of a plate 25 secured upon the top wall 2 orto any other suitable fixed supporting means. The material to bedesiccated may be delivered to the atomizing device 18 in any suitablemanner, for example, by means of a pipe 26 extending through plate 25and between the housing 15 and 20 and communicating at its lower endwith the interior of said atomizing device, for example through theenlarged housing portion 27. The centrifugal atomizer 18 may, forexample, be of the type shown and described in the patent application ofDavid D. Peebles and Arthur E. Barlow, Serial No. 527,730, filed April4, 1931, but it will be understood that the present invention is notrestricted to the use of any particular type of atomizer.

It will be evident that the introduction of hot gaseous medium throughdistributing chamber 7 and through the annular opening 12 will cause theadjacent walls or surfaces, such as partition 8 and conduit 15, as wellas the vanes 11, to tend to become heated to a relatively hightemperature, and means are therefore shown for introducing relativelycool air or other gaseous medium adjacent these walls or surfaces so asto reduce the heating of certain of these surfaces and also prevent thenon-gaseous particles within the treating chamber from coming in contacttherewith. For this purpose the plate 25 may be mounted in such manneras to be spaced somewhat above the top wall 2, for example by means ofwashers or spacers 28, so as to provide a space 29 establishingcommunication between the outside air and the interior of conduit 15,thus permitting air at relatively low temperature to be drawn in throughthis space and through the conduit 15 and opening 17. Furthermore,additional air or other gas at relatively low temperature may beadmitted through an annular passage 31 between partition 8 and anauxiliary partition 32, said annular passage communicating at its upperend with the surrounding atmosphere (or other gas source) as by means ofpipes 33 and opening into the chamber 1 at its lower end through theannular opening 34 which directly surrounds the opening 12 and whoseoutside diameter is considerably less than that of said chamber. Meanssuch as dampers 36 may be provided for controlling the inflow of airthrough the passage 31. In case the introduction of air through conduit15 and through passage 31 would be objectionable, the upper ends thereofmay be closed off from the atmosphere and may be connected by suitablepiping to any suitable means for supplying a relatively cool gas of thedesired nature.

For effecting circulation of gaseous medium in the outer portion of thetreating chamber there is shown a flue or conduit 38 communicating withsaid chamber adjacent the periphery thereof, said flue preferablyopening substantially tangentially through the side wall of the chamberand leading to the inlet side of a fan or blower 39 whose outlet isconnected to flue or conduit 41 which also opens substantiallytangentially through the side wall of the chamber 1 in a reversedirection to the flue 38, so that recirculation of gaseous mediumthrough said flues and fan tends to set up a whirling or vortical motionof the gas in the outer portion of the chamber 1, preferably in adirection opposite to that of the gas delivered to the central portionof the chamber through the vanes 11. As shown in the drawings, forexample, the vanes 11 are so disposed as to cause the hot gaseous mediumdelivered therethrough to whirl in a clockwise direction as indicated bythe arrow at A in Fig. 2, while flues 38 and 41 are so connected as tocause whirling motion inthe outer zone in a counter-clockwise direction,as in dicated by the arrow at B in said figure. The flue 88 is shown asconnected adjacent the bottom of the chamber 1 and the flue 41 is shownas connected to the chamber at a level adjacent or just below theposition of the centrifugal atomizer 18, but it will be understood thatthe invention is not restricted to the location of these flues in theseexact positions.

The means for removing from the treating chamber a portion of thegaseous medium together with the treated non-gaseous material suspendedtherein, is shown as comprising a conduit 43 opening substantiallytangentially through the said wall of chamber 1 in the same direction asthe flue 38 and at any suitable height, for example, adjacent the lowerend of said chamber, a fan or blower 44 having its inlet connected tosaid flue, and a fiue 45 connected to the outlet of said fan or blowerand adapted to deliver such gaseous medium to any suitable collectingmeans for separating or collecting the treated non-gaseous material fromsuch gaseous medium. Such collecting means may be of any suitable typeadapted for the collection of the particular material produced in theoperation of the apparatus. For example, if such material consists of afinely divided dry solid product, such apparatus may consists of cycloneseparating apparatus bag filters, or settling chambers.

Means are also shown for removing from the side and bottom walls ofchamber 1 any solid materials which may tend to momentarily depositthereon during the operation of the apparatus, such means comprisingflexible cleaning members such as chains 47 connected at 48 and 49 to asupporting frame-work 50 which is rotatably supported for movement aboutthe axis of the chamber 1. In Fig. 1 said framework is shown as mountedupon a shaft 51 rotatably mounted in bearing means 52 and 53 and drivenby means of suitable mechanism such as gears 54. In. Fig. 6, on theother hand, there is shown a possible modification in which thesupporting framework 5-0 is provided with vanes 56, whereby saidframework is adapted to be rotated by the action of the whirling gaseousmedium on said vanes. Due to the fact that chains 4'7 are connected tothe rotatable supporting frame 50 at only certain points, as at 48 andi9, and to the flexible nature thereof, they are free to swing outwardlytrifugal force into close engagement with the side walls of the chamber,and exert a flailing or jarring action thereon, to dislodge particles ofmaterial which may momentarily be deposited thereon, before suchmaterial has an opportunity to stick or accumulate in any quantity.

The desiccation of non-gaseous material in accordance with thisinvention may be carried out in the above described apparatus asfollows. Hot gaseous drying medium is continually delivered through theinclined vanes 11 into the upper central portion of the chamber 1 andadjacent the centrifugal atomizer 18, whereby such gas is caused toswirl or move about in an inner zone in the general direction indicatedat A and to also pass downwardly in such zone. At the same time, acertain amount of gaseous medium is continually withdrawn from saidchamber through conduit 43, the amount of gas so withdrawn including aquantity of the gaseous drying medium at a relatively low temperatureand augmented by a quantity of water vapor or other vapor liberated fromthe non-gaseous material as hereinafter described. Furthermore, acertain portion of the gaseous medium is continually caused torecirculate in an outer zone, in the direction indicated at B, by theaction of fan 39 which continually withdraws gas through conduit 38 anddelivers the same through conduit 41 back into the chamber with atangential component of direction and adjacent the periphery thereof.Thus a compound movement of the gaseous medium is maintained, that is,nested zones of gas are formed in which the gas is preferably caused toswirl in opposite directions.

The relatively high velocity of swirling movement of the gaseous mediumin the outer zone, together with the continual introduction of hot gasinto the inner zone, causes these zones to remain fairly well defined,although the limits of the respective zones, and the relative sizethereof, may vary considerably in different cases. Furthermore, sincegas is continually introduced into the inner zone and continuallywithdrawn from the outer zone, it is evident that gas must continuallypass from the inner zone to the outer swirling zone, and that in sodoing the gas must gradually lose its velocity of swirling in thedirection of the inner zone and then gradually acquire a velocity ofswirling in the opposite direction, so that in certain portions of thechamber there may be regions of relatively little swirling movement.However, the gas moves fairly rapidly through such regions and entersthe outer swirling zone, and the absence, or substantial absence, ofsettling of non-gaseous material within the chamber gives evidence thatthe movement of the gaseous medium, throughout the entire chamber, issufiiciently active to prevent such settling from taking place to anylarge extent.

The material to be desiccated, consisting, for example of milk or a milkproduct such as whey, is also delivered to the process continually,being introduced through pipe 26 and housing 2'7 to the centrifugalatomizing device 18, by which it is thrown outwardly, by centrifugalforce, in atomized or finely divided condition, direcly into thedownwardly swirling hot drying gas in the inner zone. This hot gasquickly heats the particles suffieiently to cause rapid evaporation ofliquid therefrom. The centrifugal atomizer is preferably rotated in thedirection of swirling movement of the gas in the inner zone, for exampleclockwise in the present case, and thus tends to induce or increase theswirling movement of the gas in such zone and directly surrounding theatomizer. The atomized particles of material are carried along with thewhirling gas and the centrifugal force thus created on said particlescauses the same to continue their outward movement and to pass outwardlythrough the inner zone of high temperature gas. While in this zone thesmall size of the particles and the movement of the gas and particlesrelative to one another both serve not only to effect a rapid transferof heat from the gas to the particles, but also to promote escape ofvapors therefrom.

The centrifugal force then causes the particles to progress outwardlythrough the region of transition between the two swirling zones and intothe outer zone, and in this movement, the particles are decelerated inone direction and then accelerated in the other direction, and are thussubjected to considerable agitation and the outward progress thereof issomewhat arrested. As the particles take up the direction of theswirling gas in the outer zone they are again subjected to centrifugalforce which prevents reentry of the particles into the high temperaturegas.

It may be pointed out here that by the time the gas reaches the outerzone it has been cooled to a relatively low temperature, by utilizationof its heat in heating the particles and in evaporating liquidtherefrom, so that it is no longer hot enough to injure the materialbeing treated. The atomized particles are, therefore, initially broughtinto contact with a gas at a relatively high temperature which, in thecase of milk or other heatsensitive organic materials, would besufficient to injure the dried material, but the particles aremaintained in contact with this high temperature gas for only a limitedperiod of time, and only during the time when their liquid content issufiiciently high to prevent burning or injury thereof. By the time theparticles are heated and partially dried to such an extent that contactwith such high temperature might be injurious they have passed out ofthis high temperature zone and into the outer zone of relatively lowertemperature. Furthermore, since the particles are subjectedsubstantially continually to the action of centrifugal force, they areprevented from subsequently re-entering the high temperature zone.

While the gas in the outer zone is at a relatively low temperature ascompared to the inner zone, it is still warm enough and of sufiicientlylow humidity to effect further evaporation of liquid from the suspendedparticles, and an important feature of this invention is that theparticles are caused to remain in suspension in this outer zone and toswirl about with the gas therein for a sufficient period of time tocomplete the desiccation thereof. course, carried along with the gasrecirculated through conduits 38 and 41 and back into the chamber. Animportant function of the recirculation is to maintain a high velocityof swirling movement of gas in the outer zone and to increase the timeduring which the particles are kept therein.

A portion of the gaseous medium containing desiccated particles insuspension therein is also continually withdrawn from the chamber 1through conduit 43 by the action of fan 44. Since this portion of thegaseous medium is removed from the outer zone it is evident that theparticles removed therewith will have been subjected to the action bothof the high temperature gas in the inner zone and also of the relativelylow tem perature gas in the outer zone, and the rate of flow of gasthrough the apparatus is so regulated, in proportion to the rate of feedof non-gaseous material thereto, that the particles so removed will havebeen dried or desiccated to the desired extent. In the apparatus shownin the drawings the rate of flow of gas through the apparatus isdetermined by the operation of fan 44, but it will be understood thatany other suitable means may be used for controlling such rate of flow.From the fan 44 the gas and desiccated particles removed from thedesiccating chamber are delivered through conduit 45 to any suitablemeans for separating the desiccated particles from the gas andcollecting the same. In the case of dried milk or whey, such separatingand collecting means may consist for example of cyclone separatingapparatus or bag filters or both.

In the above described operation it will be seen that the introductionof hot gaseous drying medium through the distributing chamber '7 andannular passage 12 will cause the conduit 15 and the partition 8 tobecome heated to such an extent that if the suspended particles of milkor whey or other organic material, or the dried or partially driedproduct thereof, were permitted to come into contact with these heatedsurfaces, such materials would be burned, discolored or otherwiseinjured. Furthermore, if the incoming hot drying medium were permittedto directly contact the means for introducing the material to be dried,including the housing means 27 and atomizer 18, so as to heat theseparts, and the suspended particles were permitted to come into contacttherewith, similar injury would result.

Some of the suspended particles are, of

However, since the fan 44 operates to always maintain a certain reducedpressure within the chamber 1, a current of relatively cool air from thesurrounding atmosphere, or other cool gaseous medium if necessary, iscontinually drawn in through the space 29 and through the annular spacebetween conduit 15 and housing 20, and enters the chamber 1 through theopening 17 at the lower end of said conduit, thus serving not only tocool the walls of said conduit and the housing 27 and atomizer 18, butalso to maintain suificient pressure below the opening 17 to preventformation of eddy currents and to force the suspended particles awayfrom, instead of toward the above mentioned parts. Furthermore, saidincoming relatively cool air may in some cases serve to maintain thefeed pipe 26 at a relatively low temperature so as to prevent unduelocalized heating of the material to be desiccated before it isdelivered in atomized condition into the desiccating chamber. Similarly,a current of relatively cool air from the surrounding atmosphere, orother cool gaseous medium if necessary, is drawn in through the annularpassage 31 between the partitions 8 and 32 and is delivered throughopening 34 into the chamber 1 just outside the incoming current of hotdrying gas and at a position removed from the side wall of the chamber,and serves to prevent heating of the partition 32 and maintain asufiicient pressure in an intermediate zone below the opening 34,between the position of introduction of hot gas through the inletopening 12 and the outer portion of the chamber, so as to preventcreation of eddy currents and to cause suspended particles to becontinually forced away from rather than toward said partition. It willbe understood that the amounts of cold air or other gas drawn in asabove described are relatively small as compared to the inflow of hotdrying gas, so that they do not materially reduce the temperature anddrying efficiency thereof, as it has been found that the introduction ofrelatively cool gas at these points, even in relatively small amounts,is decidedly advantageous in connection with the desiccation ortreatment of organic materials such as milk or whey. The amount of airdrawn in through the annular passage 31 may be controlled by adjustmentof dampers 36. In the construction shown, the amount of air drawn inthrough the conduit 15 is restricted by the relatively narrow space 29between the plate 25 and the top wall 2 of the chamber, but it will beunderstood that suitable means may be provided if desired for adjustablycontrolling the inflow of air at this point also.

The present invention is not to be understood as restricted to the useof drying gas at any particular temperature, nor to the maintenance ofany specific temperatures in the inner and outer whirling zones, but itmay be stated by way of example that in the desiccation of milk thetemperature of the incoming drying medium may be about 400 or 500 F. oreven higher, while the temperature of the gaseous medium in the outerzone and of the gaseous medium withdrawn from the desiccating chambermay be in the neighborhood of 180 to 200 F. The temperature of gas inthe inner zone may, therefore, be high enough to burn or otherwiseinjure the solids contained in milk or other organic material beingdesiccated, but injury to such material does not occur due to the shorttime of treatment of the material in this inner zone and the relativelylarge initial moisture content of the particles, and

also because of the means above described which reduces the temperatureof certain surfaces of the apparatus and prevents contact of thematerial with certain heated surfaces. The gas in the outer zone, on theother hand, is below the temperature at which the desiccated orpartially desiccated particles are susceptible to burning or injurywithin the time such particles remain in the desiccating chamber, sothat no such burning or injury can occur in either the inner or outerzone. Furthermore, the lower temperature outer zone of gas keeps theside walls of the chamber at a temperature sufliciently low to preventinjury to desiccated particles which come in contact therewith. It maybe pointed out that unduly prolonged subjection of heat-sensitivedesiccated material, such as dried milk or whey, to temperature even ashigh as those which may prevail in the outer zone of the desiccatingchamber, may cause injury thereto, and it is therefore of particularadvantage that the dried material is not allowed to accumulate orcollect within the desiccating chamber but is removed therefrom, after acertain length of time, and carried by the spent drying medium to thecollecting apparatus above mentioned.

It will be understood that the apparatus may be operated under differentconditions of pressure within the desiccating chamber, to meet varyingrequirements. For example, instead of operating at a pressure slightlybelow atmospheric as above described, pressures equal to or somewhatgreater than atmospheric pressure may be used, it being understood thatin such cases suitable means may be provided for delivering the gaseousdrying medium and also the cooling gas under suitable pressure.

In many cases hot combustion gases from a suitable furnace may be usedas gaseous drying medium, as in the apparatus above described. Suchgases may, for example, be used in the drying of milk provided the fueland the conditions of combustion are such as to avoid the presence insuch gases of a prohibitive amount of unburned carbon, ash, or otherforeign matter which would tend to contaminate or injure the desiccatedmaterial. In certain cases, however, it may be necessary or advantageousto provide other means for heating a supply of air or other gas forutilization as the drying or treating medium. For example as shown inFig. '7, the gases from a furnace 61 may be conducted by flue 62 to aheat exchanging apparatus 63 in which said combustion gases are passedin heat interchanging relationship with a stream of air or other gasdelivered through inlet flue 64, the air or other gas so heated beingthen drawn through flue 65 and delivered into the desiccating ortreating chamber in the same manner as above described. Any suitableform of heat exchanging apparatus may be: used but there is shown in thedrawing a form of apparatus comprising a chamber or housing throughwhich the air or gas to be heated is caused to pass, while the hotcombustion gases are caused to pass repeatedly and in reverse directionsthrough sets of tubes or pipes 66 extending across said chamber,suitable return chambers 67 being provided for receiving the combustiongases from one set of pipes and delivering the same to the next set. Afan or blower 69 may also be connected at any suitable point in the pathof the combustion gases, in order to induce the desired flow thereofthrough the heat exchanging apparatus. From the heat exchangingapparatus, the combustion gases which have given up a portion of theirheat,

may be conducted through conduit 71 to a stack '72 or other suitablemeans for disposal thereof. It has been found, however, that, in certaincases at least, advantageous results may be secured by recirculating aportion of the partially cooled combustion gases back through the heatexchanger, and for this purpose there is shown a by-pass flue 73 leadingfrom flue 71 back to the furnace 61, and a damper '74 for causing anydesired proportion of the gases to be diverted through said flue 73.

In Fig. '7 there are also shown means whereby the removal of gaseousmedium from the treating chamber 1 is effected solely through a singleflue 75 and a single fan or blower 76 connected thereto, and by whichthe gas so withdrawn is divided, a portion thereof passing from fan 76through flue '77, controlled by damper 78, back into the treatingchamber with a tangential component of motion, and another portionthereof passing from said fan or blower through flue 79, controlled bydamper 81, to any suitable means for separating and collecting suspendednon-gaseous material therefrom. By adjustment of dampers 78 and:81 theproportional amount of gaseous medium recirculated, in comparison withthe total amount passed through the apparatus, may be regulated asdesired so as to give the most advantageous result.

It will be understood that there is no particular reason for combiningthe means shown in Fig. 7 for eifecting recirculation and withdrawal ofgas from the treating chamber with the means shown in said figure forsupplying the hot gaseous medium, and that either of these modificationsmay be applied separately to the system shown in Figs. 1 and 2.

Another form of apparatus in accordance with this invention is shown inFigs. 8 to 12 inclusive. This form of apparatus comprises a treatmentchamber 110, preferably substantially circular in horizontalcross-section and having its axis extending in a general verticaldirection. The lower wall 111 of said chamber preferably has a raisedcentral portion, being for example conical in shape, as shown. A gaseousmedium at relatively high temperature is introduced through conduit 112which communicates with the chamber through a wall thereof, in this casethe upper wall 113. Conduit 112 is shown as arranged in alignment withthe axis of chamber 110 and depending for a substantial distancedownwardly into said chamber. In communication with the outer end ofconduit 112 there is an auxiliary chamber 114 of greater cross-sectionalarea into which hot gas can be discharged through conduit 116.

Means are also provided in this case for introducing a certain amount ofrelatively cool gas adjacent and around the periphery of the innerdischarge end of conduit 112, such means being shown as comprising acompartment 117 formed about the outer periphery of conduit 112 andcommunicating with an external conduit 118 through which cool gas may beintroduced by induced draft or by suitable means. Said conduit 118 maybe connected to any suitable source of relatively cool gas at suitablepressure. Said conduit is also preferably provided with valve means 118'for regulating the amount of gas supplied therethrough. Gas fromcompartment 117 can flow into the treatment chamber 110 through anannular orifice 119 immediately surrounding the lower end of conduit112.

The means for continually cleaning the inner walls of the chamber toprevent accumulation hollow shaft 139.

' ber upon said walls of material being treated, is shown in this caseas comprising chains 121 carried by suitable supporting rods 122, saidchains hanging down along the side walls of treatment chamber 110 andextending inwardly along the bottom wall 111 and connected to a centralpivoted member 124. Vanes 125 are provided on the supporting rod 122 forcausing rotation of said cleaning means by the swirling gas currents. Apipe 126 extends downwardly and centrally within chamber 114 and conduit112, and is rotatably journaled and supported upon the top wall ofchancber 114 in any suitable manner. The lower end of said pipe 126 isconnected to supporting rods 122 by means of a pair of concentric rings131 and 132 secured together by suitable spacer members 133, the outerring 131 being connected to rods 122 and the inner ring 132 beingconnected to pipe 126 by means of a plurality of spaced radial inclinedvanes or louvers 136. The annular space 137 between rings 131 and 132 isadjacent and aligned with the annular orifice 119, and in effect servesas a continuation of the same.

Means are also provided for introducing material to be treated into thetreatment chamber near the central axis thereof and adjacent the lowerend of conduit 112, such means being shown as comprising a rotary orcentrifugal atomizing nozzle comprising a disc 138 secured to arotatable Shaft 139 is preferably journaled within a pipe 141 whichextends concentrically within and through the pipe 126. The pipe 141 ispreferably spaced somewhat from pipe 126 so as to minimize directconduction of heat from the chamber 114 and conduit 112 to shaft 139 andthe atomizing nozzle connected thereto.

Upon the upper face of disc 138 are a plurality of circumferentiallyspaced bars 142 having their upper ends interconnected by a reenforcingring 143. Fluid material to be treated is introduced into the hollowshaft 139 through external pipe 144 and coupling 145 and flows throughsaid hollow shaft and upon the disc 138 through ports 146. Shaft 139 isconnected externally to any suitable driving means such as a steamturbine,

so that it may be rotated at a relatively high speed. The fluid materialdischarged through ports 146 is thrown outwardly along the upper face ofdisc 138 by centrifugal force and is finally atomized by impact with thebars 142. It is desirable that disc 133 should not be of greaterdiameter than the pipe 126. and in practice I prefer that said discshould be of slightly less diameter than said pipe. so that said disc isout of the direct path of the swirling gaseous medium delivered betweenthe louvers 136.

The circulating system for maintaining the outer swirling or vorticalmovement of gase ous medium within the treatment charmis shown ascomprising a conduit 14'? commrmicating tangentially with the lowerportion of said chamber and connected to the inlet side of a suitablefan or blower 148, and a conduit 149 leading from the discharge side ofsaid fan or blower and communicating tangentially with the upper portionof said chamber. The tangential relationship of conduits 147 and 149with respect to chamber 110 is such as to maintain a swirling motion inthe gaseous medium in the outer portion of said chamber by recirculationof gas therethrough, in a direction opposite to that of the swirlingmovement of hot gaseous medium introduced through conduit 112 andlouvers 136.

The hot gas conduit 116 is shown as connected to the discharge side of afan or blower 150,

through a suitable heat exchange device 151 which serves to heat the gasdelivered by fan or blower 150 to the desired temperature.

portion of the gaseous medium, with treated material in suspensiontherein, is continually removed from treatment chamber 110 by means of adischarge conduit 152 communicating with the lower portion of chamber110 near the outer periphery of said chamber, said conduit preferablycommunicating with said chamber tangentially and in the same rotativedirection as the conduit 147 above mentioned. Said discharge conduitleads to a separator 153 for separating suspended treated material fromthe discharge gas. If desired, the inlet of fan or blower 150 may beconnected to the exhaust of separator 153 so as todraw gaseous mediumthrough the desiccator and recirculate the same.

In the operation of this form of the invention the gaseous mediumdelivered by fan or blower 150 is heated by heat exchanger 151 to asuitable temperature and is delivered through conduit 116, chamber 114,and conduit 112. Said gaseous medium is introduced between the inclinedvanes or louvers 136 and is thereby given a whirling motion which servesto maintain an inner swirling zone of high temperature gas adjacent thecentral portion of chamber 110 and adjacent the centrifugal atomizer. Asbefore, the rotation of the atomizer is preferably in the same directionas the whirling motion produced by vanes 136, and may thus serve toenhance such whirling motion. The operation of fan or blower 148 alsoserves to maintain an outer zone of swirling gas in the outer portion ofthe chamber, the motion of which is in a direction opposite to that ofthe swirlin movement in the inner zone. As in the previously describedforms of apparatus, the gas passes from the inner zone to the outer zoneand is eventually discharged through conduit 152.

The material to be treated. for example milk to be desiccated. isintroduced through pipe 144 and hollow shaft 139. and is finely dividedor atomized by the centrifugal nozzle and thrown outwardly into theinner swirling zone of high temperature gas. Such material is carriedalong in suspension in thegas and is subjected to the successive actionof the high temperature gas in the inner zone and the relatively lowtemperature gas in the outer zone substantially as above described andis discharged through conduit 152 separated and collected in separator153.

The introduction of relatively cool gas into the treatment chamberthrough annular orifice 119 serves to materially reduce the operatingtemper ature of rings 131 and 132 and also serves to in crease thepressure at this point sufficiently to prevent or minimize the formationof eddy currents which would otherwise tend to carry particles ofpartially desiccated material into contact with the heated surfaces nearthe lower end of conduit 112.

As in the preceding forms of the invention, the gas introduced into theinner zone A may be heated to a temperature which would be capable ofburning or injuring such material, for example to 400 or 596 F. or.even. higher in the case of milk, as the material remains in this innerzone such a short time that it is uninjured even at this hightemperature and then enters the relatively cool gas in the outer zonewhere the treatment is completed without injury. The relatively cool gasin the outer zone also serves as before to main tain the walls of thetreatment chamber 110 at a sufficiently low temperature to preventburning or injury of particles of suspended material coming into contactwith such walls.

I claim:

1. In methods of eifecting treatment of material in suspension in agaseous medium, the steps which comprise continually introducing gaseousmedium at relatively high temperature from a conduit into a chamber andcausing said gaseous medium to swirl within said chamber about the axisthereof, introducing non-gaseous material to be treated into saidgaseous medium in said chamber, and introducing additional gaseousmedium at a temperature lower than that of the first-named gaseousmedium into an intermediate zone immediately surrounding the position ofintroduction of said first-named gaseous medium and removed from theside wall of the cham her, so as to increase the static pressure of gasin said intermediate zone.

2. In an apparatus of the class described, a treatment chamber, meansfor causing a compound whirling movement of gas within the chamber, theinner zone of whirling movement being at a relatively higher temperaturethan the outer zone, means for introducing non-gaseous material intocontact with the gas in said inner zone, and means for introducing arelatively cool gas into the chamber between the inner and outer zonesof whirling movement.

3. In an apparatus of the character described, a treatment chamber, aninflow conduit communicating with said chamber and having an innerdischarge opening, means for introducing a swirling current ofrelatively hot gas into said chamber through said conduit, means forproducing a swirling current of gas in said chamber about said firstnamed current and in the opposite direction, and means for introducing arelatively cool gas into the chamber adjacent the periphery of saidopening.

4. In a desiccator, a treatment chamber, an inflow conduit extendinginto said chamber, means for causing drying gas introduced through saidconduit to swirl about within an inner zone in said chamber, means forcausing gas in said chamber to swirl around said inner zone and in anopposite direction, and means for introducing relatively cool air intosaid chamber adjacent the inner end of said conduit.

5. The method of treating non-gaseous material in suspension in agaseous medium which comprises introducing gaseous medium at relativelyhigh temperature into the central portion of a treatment chamber, andproducing whirling movement of said gaseous medium in an inner zoneabout the axis of said chamber, maintaining whirling movementof gaseousmedium at relatively low temperature within said chamber, in an outerzone surrounding said inner zone and in a direction opposite to thewhirling movement of said inner zone, introducing non-gaseous materialin divided condition into contact with the gaseous medium in said innerzone and causing such material to pass outwardly through said zones bycentrifugal force so as to be brought successively into contact with thegaseous medium in the inner and outer zones, and continually introducingad; ditional gaseous medium at relatively low temperature in an annularregion between the inner and outer zones and immediately surrounding theposition of introduction of said high temperature gaseous medium.

6. In an apparatus for treating non-gaseous material in suspension in agaseous medium, a chamber, means for introducing non-gaseous material individed condition, with an outward component of motion into said chamberadjacent the central portion thereof, gas inlet conduit means extendinginto said chamber to a position adjacent the position of introduction ofsaid nongaseous material and provided at its inner end with an openingof considerably less diameter than said chamber, means for directing acurrent of hot gas through said conduit means and through said openinginto contact with said nongaseous material, means for maintainingswirling movement of gas and non-gaseous material in the outer portionof said chamber, partition means extending within said chamber andsurrounding and spaced from said conduit means so as to define anannular opening surrounding said first-named opening, the externaldiameter of said annular opening being considerably less than thediameter of said chamber, and means for introducing gas at a temperaturelower than said first-named gas between said conduit means and saidpartition means and through said an-' nular opening into said chamber.

eous material in suspension in a gaseous medium, a chamber, means forintroducing non-gaseous material in divided condition with an outwardcomponent of motion into said chamber adjacent the central portionthereof, gas inlet conduit means extending within said chamber to aposition adjacent the position of introduction of said non-gaseousmaterial and provided at its inner end with an opening of considerablyless diameter than said chamber, means for introducing gas at relativelyhigh temperature through said conduit means and through said openinginto said chamber, means for continually removing gas from said chamberat a position outwardly of said opening and for continuallyreintroducing such gas into the outer portion of the chamber in atangential direction so as to maintain whirling movement in the outerportion of the chamber and about the axis thereof, partition meansextending within said chamber surrounding and spaced from said inletconduit means and defining an annular opening surrounding saidfirst-named opening and of considerably less diameter than said chamber,and means for introducing gas at a temperature lower than that of saidfirst-named gas between said conduit means and said partition means andthrough said annular opening into said chamher.

8. In an apparatus for treating non-gaseous material in suspension in agaseous medium, a chamber, gas inlet conduit means extendingsubstantially axially into said chamber and provided at its inner endwith an opening of considerably less diameter than said chamber, meansfor directing a current of hot gas through said conduit means andthrough said opening into said chamber, a centrifugal atomizer mountedwithin said chamber somewhat beyond the inner end of said conduit meansand so disposed as to deliver atom-- ized material outwardly across thestream of hot gas delivered through said opening, means for maintainingswirling movement of gas and nongaseous material in the outer portion ofsaid chamber, partition means extending within said chamber andsurrounding and spaced from said conduit means so as to define anannular opening surrounding said first-named opening and having anexternal diameter considerably less than the diameter of said chamber,and means for introducing gas at a temperature lower than saidfirst-named gas between said conduit means and said partition means andthrough said annular opening into said chamber.

9. In an apparatus for treatment of non-gaseous material in suspensionin a gaseous medium, a chamber, gas inlet conduit means extendingsubstantially axially within said chamber and provided at its inner endwith an opening of considerably less diameter than said chamber, meansfor introducing gas at relatively high temperature through said conduitmeans and through said opening into said chamber, a centrifugal atomizerdisposed within said chamber and somewhat beyond the inner end of saidconduit means and mounted for rotation in such manner as to delivernon-gaseous material in divided condition outwardly and with a whirlingmotion in a plane substantially perpendicular to the axis of saidchamber and across the stream of gas introduced through said opening,means for continually removing gas from said chamber at a positionoutwardly of said opening and for continually reintroducing such gasinto the outer portion of the chamber in a tangential direction so as tomaintain whirling movement in the outer portion of the chamber and aboutthe axis thereof, and additional means for continually removing anotherportion of gas from said chamber at a position outwardly of said openingand for separating suspended particles from said last-named portion ofgas after removal thereof from said chamber.

DAVID D. PEEBLES.

